The purpose of this work is to investigate physiological and pathological aspects of the renin-angiotensin system, with emphasis on the regulation of aldosterone secretion by the zona glomerulosa of the adrenal gland. Specific areas of research include the characterization and regulation of angiotensin II receptors, the actions of angiotensin II and other regulators of aldosterone secretion, and the production and metabolism of angiotensin II. Enzyme-dispersed adrenal cells are employed for analysis of the relations between angiotensin II receptors and aldosterone production, and the interactions between angiotensin II and other factors such as ACTH, sodium, and potassium. The effects of altered electrolyte balance on angiotensin II receptors and adrenal steroid responses are studied, in particular the effects of sodium intake on the concentration of angiotensin II receptors in adrenal and smooth muscle cells. These studies are designed to clarify the control of adrenal and vascular sensitivity to angiotensin II during altered sodium balance, the mechanisms by which angiostensin II regulates the concentration of its receptors in adrenal and smooth muscle, and the activation pathways that are initiated by occupancy of angiotensin II receptors.